The present invention relates to a magnetic separator for separating particles from a fluid, comprising a collection chamber through which the fluid is arranged to flow, and a device for producing a magnetic field by means of which the particles are retained in a collector region of the collection chamber during a collection phase.
Such magnetic separators are known from the state of the art.
In the case of magnetic separators of the type mentioned hereinabove, the particles retained in the collector region of the collection chamber during the collection phase are discharged from the collection chamber during a discharge phase by flushing a fluid through the collection chamber in the reverse direction. It is disadvantageous hereby, that the considerable amount of fluid used for expelling the particles from the collection chamber is discharged, together with the particles that are to be separated, from the magnetic separator and is therefore lost.
Consequently the object of the present invention is to provide a magnetic separator of the type mentioned hereinabove wherein only a small quantity of fluid is lost when the particles that were retained in the collector region of the collection chamber are removed from the collection chamber after the collection phase.
In accordance with the invention, this object is achieved in the case of a magnetic separator having the features mentioned in the first part of claim 1 in that the magnetic separator comprises a sluice chamber having a closable inlet opening through which the particles collected in the collection chamber are transferable into the sluice chamber, and also having a closable extraction opening through which the particles are removable from the sluice chamber.
The advantage offered by the concept in accordance with the invention, is that the quantity of fluid, which is discharged together with the particles, is restricted to the volume remaining in the sluice chamber after the transfer of the particles that were collected in the collection chamber into the sluice chamber. This residual volume can be kept very small, firstly by appropriate selection of the size of the sluice chamber and secondly by appropriate selection of the quantity of particles retained in the collector region of the collection chamber during the collection phase. Moreover, due to the presence of the sluice chamber, it is possible to transfer the particles that were collected in the collection chamber out of the collector region into the interior of the sluice chamber without first having to drain the fluid requiring cleaning from the collection chamber.
The magnetic separator in accordance with the invention is particularly suitable for stripping ferrite particles from fluids, such as washings, cooling lubricants or oils, for example.
However the magnetic separator may also be used for separating ferrite particles from streams of gas and especially from air streams, for example, for cleaning the exhaust air from an abrasion dust extraction plant.
Furthermore, it has been established experimentally that non-ferrite particles, especially very fine aluminium particles, are also separable from a fluid by means of the magnetic separator in accordance with the invention.
The magnetic separator in accordance with the invention may be employed as a main stream magnetic separator in a circulating fluid system, for example in a scouring, cooling lubricant, or oil circulation system.
As an alternative thereto, it is also possible to employ the magnetic separator in a bypass line, for example, for bath maintenance purposes in washing baths or cooling lubricant plants.
The magnetic separator in accordance with the invention is easily integratable into fluid lines and reliably prevents the storage and/or operational containers in a fluid circulating system from silting up.
In a preferred embodiment of the magnetic separator, the sluice chamber is disposed below the collection chamber. This thereby ensures that the particles that are retained in the collector region of the collection chamber will fall into the sluice chamber under the effect of gravity after the magnetic field has been switched off or removed.
In principle, the sluice chamber could have any shape, cylindrical for example.
However, it is preferred to have a sluice chamber which tapers, preferably conically, towards the extraction opening.
In order to enable the sluice chamber to be easily emptied, the extraction opening is preferably disposed at the lower end of the sluice chamber so that the particles will fall out of the sluice chamber and into a collection container disposed therebelow due to the effect of gravity after the extraction opening has been opened.
Furthermore, for the purposes of completely emptying the sluice chamber, it is expedient for the extraction opening to extend over the entire base of the sluice chamber.
Furthermore, complete emptying of the sluice chamber can be assisted by providing the inner surface of the wall of the sluice chamber at least partially with a non-stick coating, preferably with a non-stick coating of polytetrafluoroethylene.
In principle, any form of closure device could be used for closing the inlet opening of the sluice chamber.
In a preferred embodiment of the magnetic separator, provision is made for the inlet opening to be closable by means of a pivotal flap.
In principle, any form of closure device could also be used for closing the extraction opening of the sluice chamber.
In a preferred embodiment of the magnetic separator, provision is made for the extraction opening to be closable by means of a slider.
As already mentioned, the maximum volume of fluid, which is discharged by the sluice chamber together with the particles, corresponds to the difference between the volume of the interior of the sluice chamber and the volume of the particles transferred into the sluice chamber.
In order to keep the volume of the fluid that is discharged together with the particles as small as possible, it is therefore of advantage if the volume of the interior of the sluice chamber substantially corresponds to the volume of particles collected in the collection chamber during the collection phase.
In principle, the fluid could flow through the collection chamber in any arbitrary direction, particularly in any horizontal or vertical direction.
In a preferred embodiment of the magnetic separator, provision is made for the fluid to flow from top to bottom through the collection chamber. It is thereby ensured that the inflow of the fluid into the collection chamber will be arranged above the collector region so that the particles will not be able to fall from the collector region into the fluid inlet feed.
It is expedient if the magnetic separator comprises guide means for producing a substantially helical flow through the collection chamber. Due to the helical flow, there thus arises a so-called cyclone effect, i.e. the particles being separated, which generally have a greater density than the fluid, will be accelerated towards the (relative to the helical axis of the helical stream) radially outwardly located boundary walls of the collection chamber by the centrifugal forces effective thereon. Thus, by virtue of the cyclone effect, separation of the particles that are to be separated from the fluid will commence immediately, and the particles requiring separation then only need to be retained on said radially outward boundary walls.
In this case, it is particularly expedient for the device for producing the magnetic field to be arranged close to the radially outer boundary walls of the collection chamber and for it to produce a magnetic field by means of which the particles will be retained on the radially outer boundary walls of the collection chamber.
The magnetic separator is particularly easy to manufacture and arrange in space-saving manner if the collection chamber has a substantially cylindrical shape.
For the purposes of producing the cyclone effect which has already been described hereinabove, it is advantageous if the collection chamber has an inlet feed through which the fluid flows into the collection chamber substantially tangentially relative to the inner surface of the wall of the collection chamber.
If, advantageously, the magnetic separator comprises a return feed which flows into an aperture opening in the collection chamber and extends upwardly from the aperture opening, then the effect will thereby be achieved that the particles or other objects sinking into the collection chamber cannot settle in the return feed.
It is particularly expedient if a central axis of the return feed in the vicinity of the aperture opening includes an angle of at least approximately 30xc2x0 with the horizontal. Such a return feed is steep enough to reliably prevents particles or other objects from settling in the return feed.
The device for producing the magnetic field may, for example, comprise electromagnets which can be turned off after the collection phase so as to enable the particles to be transferred into the sluice chamber. However, such electromagnets may exhibit remanence, i.e. a residual magnetic field which continues to exist after the current through the coil has been switched off, thereby possibly hindering the complete removal of the particles from the collector region.
In a preferred embodiment of the separator in accordance with the invention, provision is therefore made for the device for producing the magnetic field to comprise at least one permanent magnet element.
In order to enable the particles to be transferred from the collector region into the sluice chamber after the collection phase, provision is advantageously made for the device for producing the magnetic field to comprise at least one magnet element which is movable relative to the collection chamber.
One particularly simple method of implementing this feature is obtained when the magnet element is made pivotal relative to the collection chamber.
Furthermore, it is advantageous if the magnet element is disposed on a mounting element of ferromagnetic material. By virtue of the magnetic influence of the ferromagnetic material in the mounting element, the magnetic field produced by the magnet element will be strengthened and the extent thereof within the collection chamber will be increased. This thereby enables very fine particles as well as particles consisting of a high density ferrite material to be retained securely in the collector region.
In a preferred embodiment of the magnetic separator in accordance with the invention, provision is made for the magnetic separator to comprise a receptacle for an air-cushion, said receptacle communicating with the collector region of the collection chamber. This air-cushion is primed to the pressure of the fluid during the collection phase in which the collection chamber is traversed by the fluid requiring cleaning. Since the fluid is advanced through the collection chamber by means of a fluid pump during the collection phase, the pressure of the fluid during the collection phase is higher than atmospheric pressure. If the flow of fluid into the collection chamber is blocked at the end of the collection phase, then the air-cushion will expand thereby triggering a pulse-like movement of the fluid column in the collector region of the collection chamber thus causing the particles which have collected in the collector region to be detached.
For the purposes of creating this detachment effect produced by the expanding air-cushion, it is particularly expedient if the air cushion is disposed above the collector region so that the detached particles will move downwardly under gravitational force in the same sense as the pulse-like movement triggered by the expansion of the air cushion.
In a preferred embodiment of the magnetic separator in accordance with the invention, the receptacle for the air cushion comprises a substantially cylindrical accommodating tube.
It is particularly expedient if the longitudinal axis of the accommodating tube is aligned towards the collector region so that the casing wall of the accommodating tube will steer the pulse-like movement triggered by the expansion of the air-cushion towards the collector region.
If the magnetic separator only comprises one single collection chamber, then the stream of fluid through the magnetic separator must be interrupted between two collection phases for the purposes of transferring the particles collected in the collector region into the sluice chamber (sedimentation phase).
A continuous separating process can be effected in the magnetic separator if, advantageously, the magnetic separator comprises at least two collection chambers through which the fluid is arranged to flow alternately. Thus, at any one time, one of the collection chambers is in its collection phase, whilst the other collection chamber is in its sedimentation phase wherein the particles are transferred from the collector region into the sluice chamber.
In principle, it is possible for the two collection chambers to be housed in mutually spatially separated magnetic separator units. This has the advantage that these magnetic separator units can either be used individually for a discontinuous separating process, or, they can be connected together for effecting a continuous separating process and thus the utilisation thereof is very flexible.
By contrast however, a magnetic separator for a continuous separating process is particularly space-saving if the at least two collection chambers are arranged in a common housing.
Such a magnetic separator is particularly easy to manufacture and arrange in space-saving manner if, advantageously, provision is made for the common housing to comprise a substantially cylindrical section.
Further features and advantages of the invention form the subject matter of the following description and diagrammatic illustration of embodiments thereof.